1. Field of the Invention
This invention relates to improvements in a torque limiter. More particularly, the present torque limiter uses a plurality of ball bearings that are retained in a ball cage and the ball bearings are compressed to create frictional drag on opposing flat plate surfaces.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In some military vehicles the gun turret is rotated by personnel turning a crank that rotates the turret. The crank rotates a pinion or chain that turns the rack of the turret. When the turret does not move freely the personnel will typically apply more force that results in damaging the pinion, chain and or the rack. Repairing these components can be expensive and requires that the vehicle be taken out of service while the repair is being made. The torque limiter for a gun turret in the pending application connects between the crank and the drive train to allow the crank to turn without applying excessive torque forces on the pinion, chain and or the rack.
Several products and patents have been issued on ball bearing torque limiters without providing an acceptable solution. Exemplary examples of patents covering these products are disclosed herein.
U.S. Pat. No. 3,542,162 issued Nov. 24, 1970 to Richard H. Karr and U.S. Pat. No. 5,190,499 issued Mar. 2, 1993 to Keiji Mori et al both disclose torque limiting devices. In the case of '162 the torque limiter is for power transmission and the ball bearings roll in a recessed track. In the case of '499 the torque limiter is for an automobile mirror to prevent moving the mirror past a stop. The ball bearings are pressed with compression springs to maintain the desired torque limit. These patents do not operate to reduce the amount of force from a person turning a gun turret and all of the ball bearings follow the same track whereby the balls can create a single track.
U.S. Pat. No. 4,176,733 issued Dec. 4, 1979 to Robert G. Twickler discloses a combination no-back brake and torque limiter assembly. This assembly provides the dual function of a brake and a torque limiter. The ball bearings ride in a tapered track and depending upon the location of the ball(s) within the track, the amount of slip to the torque limiter is variable. As the ball moves higher in the track the torque amount is increased. This patent does not provide a constant torque limit without a braking function.
U.S. Pat. No. 4,898,265 issued to Jeffrey D. Metcalf on Feb. 6, 1990 discloses a torque limiter. This patent uses a series of springs that axially load the friction brake to limit the torque. While this patent discloses a torque limiter, the slipping of the torque limiter is through friction brakes that can create dust and debris that can cause future harm to the torque limiter and the torque limit is not transmitter through the ball bearings.
What is needed is a torque limiter that is designed for use by a manual operator and does not result in the generation of brake dust, debris or other contaminants. This application provides the solution where the friction is caused by compression of multiple ball bearings between two flat surfaces.